Mattison coached with new Wolverines coach Brady Hoke under Jack Harbaugh at Western Michigan and Lloyd Carr at Michigan.
Pagano will be officially introduced as the defensive coordinator at a news conference Wednesday.
Pagano, who has a reputation as an aggressive defensive coach, was the University of North Carolina's coordinator in 2007. He has previous NFL stints as a secondary coach with the Oakland Raiders and the Cleveland Browns.
"He's completely, in my view, a great coach and deserves it," Ravens cornerback Josh Wilson told the Carroll County Times. "He knows what he's doing. Chuck is going to be a great defensive coordinator. It's not going to be any kind of, 'Can he get the job done?' Everybody knows he can handle it. It's going to be like nothing ever changed."
Cornerback Fabian Washington, who has played under Pagano for five years (two in Oakland), called the move "way past overdue."
"Chuck is the right guy for the job," Washington told The Baltimore Sun. "If anybody deserves that job, it's Chuck. That guy is one of the best football coaches I've ever been around."
Mattison took over as the Ravens' defensive coordinator after Rex Ryan departed Baltimore to become the New York Jets' head coach before the 2009 season. The Ravens' defense ranked in the top 10 in the NFL during both of Mattison's seasons as coordinator.
The Associated Press contributed to this report.